In certain machine tools, such as semi-automatic lathes, center lathes, or drill presses, despite the precision of the machines, it is difficult to perfectly align the axis of the element supporting the boring tool with the axis of the bore to be produced. One of the main causes of these difficulties arises from temperature variations caused by heating, which take the form of uncontrollable expansion phenomena.
To ensure good alignment between the boring tool and the bore, it is known that a floating chuck can be used which automatically and geometrically compensates for errors in alignment as well as angularity.
In known fashion, the tool-carrying bush is coupled to the body of the chuck by an Oldham coupling and moves on bearings associated with this coupling. The chuck can therefore shift laterally relative to the body, while maintaining perfect parallelism with the axis of the chuck.
Some boring tools have a central channel, allowing passage of an irrigating fluid. The liquid brought to the end of the chuck shank must be transferred to the bush which serves to hold the tool. Such a transfer is difficult to accomplish in a simple and efficient manner, in view of the requirements for radial and angular displacement between the body and the bush. To ensure a good seal, without interfering with the ability of the bush to shift out of alignment, it is necessary to employ an assembly of joints with a complex structure, including tapered connections. These parts are subject to wear and must be replaced frequently.
To overcome this disadvantage, a method has been devised for providing a passageway for the fluid in the body of the bush by using a flexible, fluid tight connecting tube. However, this tube, because of the materials used, cannot withstand high pressure. In addition, under the influence of the working pressures transmitted by the tool, it becomes a stiffening element which interferes with radial displacement, with consequent angular misalignment of the body and the bush.